Troubleshooting Guide • Updated Sep 8, 2025
Fridge Not Defrosting? Causes, DIY Checks, and When to Call a Pro
From the technicians at Advance Appliance Ltd serving Edmonton, Calgary, and Red Deer.
Quick signs your fridge isn’t defrosting
- Freezer back wall is packed with snow-like frost.
- Freezer stays cold, but fresh-food section turns warm.
- Fan noise grows louder or stops (ice blocking airflow).
- Water under crispers after a partial thaw/refreeze.
- Error codes related to defrost or sensors (on some models).
Why it matters
Without defrost, the evaporator coils ice up, choking airflow. Food temps rise, compressors overwork, and energy bills climb. A prompt fix protects food safety and the appliance.
Top causes (and what they mean)
1) Defrost heater failure
The heater can’t melt frost, so ice steadily builds. Often shows as a full snow blanket over the evaporator.
2) Defrost thermostat / bimetal
If stuck open, the heater never energizes. If stuck closed, it can overheat and trip safeguards.
3) Control board or defrost timer
Newer models use boards; older ones use timers. If schedules don’t trigger, frost wins.
4) Thermistor / defrost sensor
Bad readings confuse the board. Result: sporadic or zero defrost cycles.
5) Wiring & connectors
Heat and moisture can oxidize or burn terminals—no power to the heater.
6) Door gaskets
Leaky seals pull in humid air, growing frost faster than the system can melt it.
Tech tip: If you recently replaced a board or sensor and re-icing is fast, recheck connectors, harness routing, and sensor placement on the coil.
DIY checks (safe and simple)
- Unplug first. Remove the freezer rear panel to view the evaporator.
- Inspect frost pattern. Even, snow-like frost = defrost fault; thick ice block on one corner may be a sealed system issue (call a pro).
- Forced defrost test. Many models allow a service mode to activate the heater. Listen for faint sizzle; avoid touching live parts.
- Test the heater. With a multimeter, disconnect leads and check for continuity.
- Test the defrost thermostat/thermistor. Cold-closed thermostats should read continuity; thermistor ohms should match the brand chart.
- Check door gaskets. Look for tears, warping, or gaps. Close a paper strip in the door; if it slides out easily, the seal is weak.
Symptoms → Likely causes → Actions
| Symptom | Likely Cause | What to Do |
|---|---|---|
| Freezer wall covered in snow-like frost | Defrost heater failure; stuck-open thermostat; timer/board not initiating | Forced-defrost test; test heater continuity; test thermostat/thermistor; inspect control/timer |
| Fresh-food warm, freezer OK | Airflow blocked by ice on evaporator | Defrost system diagnosis; avoid propping doors open long-term |
| Re-icing quickly after manual defrost | Sensor misreadings; wiring/connector issues; door gasket leaks | Verify thermistor values, connector integrity, and gasket seal tension |
| Breaker trips or burnt smell | Shorted heater or damaged wiring | Unplug immediately and book service |
When to call a professional
Call a certified technician if breakers trip, there’s a burning smell, error codes persist, or ice returns quickly after a manual defrost. For fast, local help, book trusted refrigerator repair with Advance Appliance Ltd.
Service areas: Edmonton, St. Albert, Sherwood Park, Leduc, Spruce Grove, Calgary & area (Airdrie, Cochrane, Chestermere, Okotoks), and Red Deer & nearby communities.
FAQs
How long should a defrost cycle last?
Typically 10–30 minutes, model dependent. Some boards adapt timing based on door openings and compressor run-time.
Will unplugging overnight fix it?
It can temporarily restore airflow by melting ice, but the root cause (heater/thermostat/board) still needs diagnosis.
Is a hair dryer safe to melt ice?
No. It risks electric shock and component damage. Use time and ambient air only, or hire a professional.